On Labor Day 2013, fittingly, athlete Diana Nyad, 64, became the first person to swim from Havana, Cuba, to the Florida Keys without a shark cage. “If you say to yourself ‘find a way,’ you’ll make it through,” Nyad said from Key West on Tuesday. Her previous four attempts at the more than 100-mile feat fell short due to injury or weather. In an exclusive interview with Reader’s Digest on the eve of her second attempt in 2011, Nyad said, “I don’t think any ocean swimmer has ever been this prepared physically or mentally.” Read more from Nyad and watch an inspiring video of her preparation below.

Under the pale light of a half-moon at midnight, Diana Nyad’s agonized groans carried across the water to her support boat 18 feet away. The vessel drifted on the choppy surface, and her crew looked on, hoping she’d rally and find light on the other side of this darkness.

It was August 10, 2011. Though Nyad had instructed her 11-person team of navigators, doctors, and trainers not to tell her how many miles were left in her epic swim, the facts were as stark as the night that lay ahead. Nyad had been in the water, stroking arm over arm, turning her head to breathe once every second, for more than 20 hours. She was dozens of miles into her quest to complete a 103-mile swim from Cuba to Key West, Florida, but still closer to the start than the finish.

Because of the currents in the Florida Straits, Nyad would have to last 60 hours — if everything went perfectly. So far, hardly anything had gone right.

“We got a forecast of nice, calm, light wind, but that didn’t happen,” Nyad recalled later. “We had rough seas all over the place.”

The waves swelled. Her chest was corseted by asthma; her shoulder was injured. She had swum into a field of jellyfish that made a meal of her and covered her skin in a rash of painful welts. She was cold and nauseated. Even her goggles kept fogging. There were 50 more miles to go to reach land and 5,500 feet of ocean beneath her, and she was digging even deeper than that into her own soul just to keep surging forward. All these numbers and measurements to process. And one more: In two weeks, she was going to turn 62 years old.